1. Field of the Invention
The present invention relates to a liquid discharge method and a liquid discharge apparatus.
In this respect, the term xe2x80x9crecordingxe2x80x9d in the description of the present invention means not only the provision of images having characters, graphics, or other meaningful representation, but also, the provision of those images that do not present any particular meaning, such as patterns.
2. Related Background Art
There has been known the so-called bubble jet recording method, which is an ink jet recording method whereby to form images on a recording medium by discharging ink from discharge ports using acting force exerted by the change of states of ink accompanied by the abrupt voluminal changes (creation of bubbles), and to form images on a recording medium by the discharged ink that adheres to it. For the recording apparatus that uses the bubble jet recording method, it is generally practiced to provide, as disclosed in the specifications of Japanese Patent Publication No. 61-59911 and Japanese Patent Publication No. 61-59914, the discharge ports that discharge ink, the ink paths conductively connected to the discharge ports, and heat generating members (electrothermal converting members) arranged in each of the ink paths as means for generating energy for discharging ink.
In accordance with such recording method, it is possible to record high quality images at high speeds with a lesser amount of noises. At the same time, the head that executes this recording method makes it possible to arrange the discharge ports for discharging ink in high density, with the excellent advantage, among many others, that images are made recordable in high resolution, and that color images are easily obtainable by use of a smaller apparatus.
Further, in the specifications of Japanese Patent Laid-Open Application No. 62-48585 and Japanese Patent Laid-Open Application No. 8-169116, there is disclosed a liquid jet recording head provided with energy generating members formed by a plurality of electrothermal converting members arranged in the respective ink flow paths to make it possible to present gradational representation. Also, in the specification of Japanese Patent Laid-Open Application No. 8-183180, a method is disclosed for giving pulses in order to modulate the discharge amounts stably.
However, if it is intended to increase the discharge amount by driving plural electrothermal converting members which are provided together in one ink flow path as in the above conventional example, the discharge speed is also increased at the same time eventually, or if it is intended to decrease the discharge amount, the discharge speed-is decreased simultaneously. Here, the relationship between the discharge amount and the discharge speed is almost proportional. Therefore, when the discharge amount should be decreased, the discharge instability may take place due to the slowdown of the discharge speed. This tendency is more conspicuous under the low temperature environment in particular. In the worst case, there is a fear that the disabled discharge occurs inevitably.
On the other hand, when the discharge amount should be made larger, the discharge speed becomes extremely faster. As a result, the dot configuration is disturbed on an image or the dot dispersion phenomenon may take place due to the satellite dots to cause the image degradation or the rebounding phenomenon of ink occurs when it is impacted on the surface of a recording sheet. The rebounded ink adheres to the surface of the recording head, hence affecting the stability of liquid discharges in some cases.
The present invention is designed in consideration of the problems of the conventional techniques of the method for forming discharge liquid droplets by driving a plurality of electrothermal converting members at a time. It is an object of the invention to materialize a discharge method capable of obtaining desired images recorded in higher quality.
It is another object of the invention to provide excellent techniques to overcome the difficulty lying in the technical background to make it possible to specify and obtain the amount of a larger droplet two to three times the amount of a smaller (discharged) droplet even when the smaller droplet is formed by use of one electrothermal converting member, while the larger droplet is formed by use of plural electrothermal converting members for the provision of images in good quality with the droplets having different discharge amounts, larger and smaller as required, respectively.
It is still another object of the invention to provide a discharge method and a recording method capable of forming high quality images by a desired stability of shooting accuracy with the uniform discharge speeds of the methods whereby to make formations different by driving plural electrothermal converting members altogether.
The present inventors hereof have ardently studied every aspect related to the development of an ink jet recording apparatus capable of printing images in higher quality. As a result, giving attention to the flow directivities of liquid (or gas) flow in the directions outgoing and ingoing from the ink flow paths at the liquid discharge ports along with the development and contraction of bubbles by the function of electrothermal converting members, the inventors hereof have made theoretical analyses and found that discharge amounts are made greatly changeable without causing the discharge speeds to vary too much by making the arrangement so that the components formed by the plural electrothermal converting members in the direction (discharging direction) outgoing from the ink flow paths do not intervene to change the discharge speeds themselves, while the components in the direction opposite to the flow direction are allowed to intervene. On the basis of such finding, the inventors hereof have conducted experiments and confirmed that the timing of a first driving pulse and that of a second driving pulse are deviated up to the level of 10 xcexcsec order which has never been expected in the conventional art. As a result, it has been found that there exists an area where the discharge amount is made changeable, while the ink droplet discharging velocity is substantially constant (a range of timing deviation of 10 xcexcsec to 20 xcexcsec, for example).
Hence, the liquid discharge method of the present invention is designed to use a driving condition in a range where the discharge speed of droplets is made substantially constant, while the amount of droplet is made changeable with the timing difference of driving when droplets are discharged by driving a plurality of the electrothermal converting members one after another. These features are shared by the liquid discharge method of the invention that makes the discharge amount changeable.
Also, such timing difference is in a range where the discharge speed of droplets is made substantially constant, and also, the discharge amount is allowed to take the minimum value to the maximum value thereof.
Also, the timing difference is in a range to enable the discharged droplet to be formed as one dot on the surface of the recording medium.
Also, the timing difference is in a range where a second liquid droplet discharged by a second pulse catches up and collides with a first liquid droplet discharged by a first pulse before arriving at the surface of a recording medium, and these droplets are allowed to impact on the surface of the recording medium as one droplet.
Also, such timing difference is characterized in that while the meniscus formed on the discharge port by a first liquid droplet discharged by a first driving pulse is retracted, a second driving pulse is applied.
Also, the waveforms of pulses are different for the first and second pulses.
Also, the energy generating members are arranged in series in the direction of liquid flow in each of the liquid flow paths.
Also, the energy generating members are arranged in parallel with the flow direction of liquid in each of the liquid flow paths.
Also, the feature of the present invention is represented by a liquid discharge method for a liquid discharge head using a nozzle provided with at least two electrothermal converting members (heaters) in the interior thereof for discharging ink from the nozzle by driving the electrothermal converting members in accordance with recording signals for recording one pixel, which comprises the step of discharging ink by setting the timing of driving the other one of the electrothermal converting member subsequent to one of them driven during the period of the meniscus of ink supplied in the nozzle being present in a position retracted from the opening end of the nozzle. During this period, it is possible to make the ink discharge amount changeable without changing the discharge speed too much.
Then, it may be possible to discharge ink by controlling the timing in accordance with the gradational information contained in the recording signals for the formation of pixels having different ink amounts. In this manner, the print quality is stabilized even when the ink discharge amount is controlled in accordance with the gradational information for printing.
Also, the timing is delayed relatively during the period of the meniscus of ink supplied in the nozzle being present in the position retracted from the opening edge of the nozzle for the formation of pixels having a larger amount of ink. In this manner, while suppressing the discharge speed lower, the ink discharge amount can be increased.
It is preferable to arrange the electrothermal converting member driven earlier on the opening edge side of the nozzle, and the electrothermal converting member driven later on the rear side of the nozzle.
It is preferable that the electrothermal converting member driven earlier is comparatively smaller, and the electrothermal converting member driven later is comparatively larger.
Also, the feature of the present invention is represented by a liquid discharge method for a liquid discharge head using a nozzle provided with at least two electrothermal converting members in the interior thereof for discharging ink from the nozzle by driving the electrothermal converting members in accordance with recording signals for recording one pixel, which comprises the steps of forming pixel having a smaller amount of ink by driving only one of electrothermal converting members in the nozzle to discharge ink; and forming pixel having a larger amount of ink by driving one of the two electrothermal converting members in the nozzle, and after that, driving the other one of the electrothermal converting members to discharge ink for the formation of pixel having a large amount of ink by the timing set during the period of the meniscus of ink supplied in the nozzle being present in the position retracted from the opening edge of the nozzle. In this way, it becomes possible to effectively perform printing for the formation of pixels having a smaller amount of ink and those having a larger amount of ink, thus stabilizing the print quality.
Also, the feature of the present invention lies in the provision of a liquid discharge method for a liquid discharge head using a nozzle provided with at least two electrothermal converting members in the interior thereof for discharging ink from the nozzle by driving the electrothermal converting members in accordance with recording signals for recording one pixel, which comprises the step of driving one of the electrothermal converting members when recording one pixel, and driving the other one of the electrothermal converting members subsequent to the one of them being driven at the timing making the ink discharge amount minimum substantially.
Also, another feature of the present invention is represented by a liquid discharge method for a liquid discharge head using a nozzle provided with at least two electrothermal converting members in the interior thereof for discharging ink from the nozzle by driving the electrothermal converting members in accordance with recording signals for recording one pixel, which comprises the step of driving one of the electrothermal converting members when recording one pixel, and driving the other one of the electrothermal converting members subsequent to the one of them being driven at the timing to create bubble in ink by driving of the other one of the electrothermal converting members when the volume of the bubble created in ink by the driving of the one of the electrothermal converting members becomes maximum substantially.
Here, in either cases, the electrothermal converting members are arranged in positions having different distances from the opening edge of the nozzle, respectively.
Also, in some cases, the electrothermal converting member having the shorter distance from the opening edge is driven earlier, and after that, the electrothermal converting member having the longer distance from the opening edge is driven at such timing, and vice versa.
Also, the electrothermal converting member having the shorter distance from the opening edge has a smaller area than the electrothermal converting member having the longer distance from the opening edge in some case.
Also, in some other case, the areas of the electrothermal converting member having the shorter distance from the opening edge and the electrothermal converting member having the longer distance from the opening edge are the same.
It is preferable to arrange so that the electrothermal converting member having the shorter distance from the opening edge is provided with an area for the value of discharge speed v/discharge amount Vd of the individual ink discharge from the electrothermal converting member to be reduced as the distance is increased.